Convert openpower-ubi-fs to a distro feature

As with MRW the use of the UBI image scheme is distro policy.
Convert the existing machine feature to a distro feature.

Enable the new distro feature on the systems that use
it(Witherspoon).

Add a distro override and fix-up MF checks to use this override
instead for improved readability.

Change-Id: I57f3bc244523eff5bc043caff8365e334d98cb30
Tested: Built a witherspoon image and validate manifest
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/common/recipes-phosphor/packagegroups/packagegroup-op-apps.bb b/common/recipes-phosphor/packagegroups/packagegroup-op-apps.bb
index d4e8d20..b3783d8 100644
--- a/common/recipes-phosphor/packagegroups/packagegroup-op-apps.bb
+++ b/common/recipes-phosphor/packagegroups/packagegroup-op-apps.bb
@@ -45,10 +45,15 @@
 SUMMARY_${PN}-flash = "OpenPOWER Flash"
 RDEPENDS_${PN}-flash = " \
         obmc-control-bmc \
-        ${@mf_enabled(d, 'openpower-ubi-fs', \
-            'openpower-software-manager', \
-            'obmc-flash-bios obmc-mgr-download obmc-op-flasher')} \
+        obmc-flash-bios \
+        obmc-mgr-download \
+        obmc-op-flasher \
         "
+RDEPENDS_${PN}-flash_df-openpower-ubi-fs = " \
+        obmc-control-bmc \
+        openpower-software-manager \
+        "
+
 
 SUMMARY_${PN}-system = "OpenPOWER System"
 RDEPENDS_${PN}-system = " \